port_allocator.go

/*
 * Copyright (C) 2016 Red Hat, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy ofthe License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specificlanguage governing permissions and
 * limitations under the License.
 *
 */

package portallocator

import (
	"errors"

	"github.com/safchain/insanelock"
)

var (
	// ErrInvalidPortRange invalid port range
	ErrInvalidPortRange = errors.New("Invalid port range")
	// ErrNoPortLeft no port left in the range
	ErrNoPortLeft = errors.New("No free port left")
)

// PortAllocator describes a threads safe port list that can be allocated
type PortAllocator struct {
	insanelock.RWMutex
	MinPort int
	MaxPort int
	PortMap map[int]bool
}

// Allocate returns a new port between min and max ports. Call the given function
// that will validate the allocation
func (p *PortAllocator) Allocate(fnc func(int) error) (int, error) {
	p.Lock()
	defer p.Unlock()

	for i := p.MinPort; i <= p.MaxPort; i++ {
		if _, ok := p.PortMap[i]; !ok {
			if err := fnc(i); err == nil {
				p.PortMap[i] = true
				return i, nil
			}
		}
	}
	return 0, ErrNoPortLeft
}

// Release a port
func (p *PortAllocator) Release(i int) error {
	p.Lock()
	defer p.Unlock()

	if i < p.MinPort || i > p.MaxPort {
		return ErrInvalidPortRange
	}

	delete(p.PortMap, i)
	return nil
}

// ReleaseAll ports
func (p *PortAllocator) ReleaseAll() {
	p.Lock()
	defer p.Unlock()

	p.PortMap = make(map[int]bool)
}

// New creates a new port allocator range
func New(min, max int) (*PortAllocator, error) {
	if min <= 0 || max < min {
		return nil, ErrInvalidPortRange
	}

	return &PortAllocator{
		MinPort: min,
		MaxPort: max,
		PortMap: make(map[int]bool),
	}, nil
}